Feature fill with nucleation inhibition

ABSTRACT

Described herein are methods of filling features with tungsten, and related systems and apparatus, involving inhibition of tungsten nucleation. In some embodiments, the methods involve selective inhibition along a feature profile. Methods of selectively inhibiting tungsten nucleation can include exposing the feature to a direct or remote plasma. Pre-inhibition and post-inhibition treatments are used to modulate the inhibition effect, facilitating feature fill using inhibition across a wide process window. The methods described herein can be used to fill vertical features, such as in tungsten vias, and horizontal features, such as vertical NAND (VNAND) wordlines. The methods may be used for both conformal fill and bottom-up/inside-out fill. Examples of applications include logic and memory contact fill, DRAM buried wordline fill, vertically integrated memory gate and wordline fill, and 3-D integration using through-silicon vias.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of and claims priority to U.S.application Ser. No. 14/866,621, titled “FEATURE FILL WITH NUCLEATIONINHIBITION,” filed Sep. 25, 2015, which claims the benefit of U.S.Provisional Application No. 62/058,058, titled “FEATURE FILL WITHNUCLEATION INHIBITION,” filed Sep. 30, 2014, each of which isincorporated herein by this reference and for all purposes.

BACKGROUND

Deposition of conductive materials using chemical vapor deposition (CVD)techniques is an integral part of many semiconductor fabricationprocesses. These materials may be used for horizontal interconnects,vias between adjacent metal layers, contacts between first metal layersand devices on the silicon substrate, and high aspect ratio features. Ina conventional tungsten deposition process, a substrate is heated to apredetermined process temperature in a deposition chamber, and a thinlayer of tungsten-containing materials that serves as a seed ornucleation layer is deposited. Thereafter, the remainder of thetungsten-containing material (the bulk layer) is deposited on thenucleation layer. Conventionally, the tungsten-containing materials areformed by the reduction of tungsten hexafluoride (WF₆) with hydrogen(H₂). Tungsten-containing materials are deposited over an entire exposedsurface area of the substrate including features and a field region.

Depositing tungsten-containing materials into small and, especially,high aspect ratio, features may cause formation of seams and voidsinside the filled features. Large seams may lead to high resistance,contamination, loss of filled materials, and otherwise degradeperformance of integrated circuits. For example, a seam may extend closeto the field region after filling process and then open duringchemical-mechanical planarization.

SUMMARY

Described herein are methods of filling features with tungsten, andrelated systems and apparatus, involving inhibition of tungstennucleation. In some embodiments, the methods involve selectiveinhibition along a feature profile. Methods of selectively inhibitingtungsten nucleation can include exposing the feature to a direct orremote plasma. Pre-inhibition and post-inhibition treatments are used tomodulate the inhibition effect, facilitating feature fill usinginhibition across a wide process window. The methods described hereincan be used to fill vertical features, such as in tungsten vias, andhorizontal features, such as vertical NAND (VNAND) wordlines. Themethods may be used for both conformal fill and bottom-up/inside-outfill. Examples of applications include logic and memory contact fill,DRAM buried wordline fill, vertically integrated memory gate andwordline fill, and 3-D integration using through-silicon vias.

One aspect relates to a method including providing a substrate includinga feature having one or more feature openings and a feature interior;selectively inhibiting tungsten nucleation in the feature such thatthere is a differential inhibition profile along a feature axis;modulating the differential inhibition profile to form a modifieddifferential inhibition profile; and selectively depositing tungsten inthe feature in accordance with the modified differential inhibitionprofile.

In some embodiments, selectively inhibiting tungsten nucleation in thefeature includes exposing the feature to a direct plasma while applyinga bias to the substrate. A direct plasma may include one or more ofnitrogen, hydrogen, oxygen and carbon activated species. In someembodiments, the plasma is nitrogen-based and/or hydrogen-based. In someembodiments, selectively inhibiting tungsten nucleation in the featureincludes exposing the feature to a remotely-generated plasma. In someembodiments, the method involves depositing a tungsten layer in thefeature prior to selective inhibition.

Examples of modulating the differential inhibition profile includesoaking the feature in a reducing agent or tungsten-containing agent,annealing the substrate, exposing the feature to a hydrogen-containingplasma, and exposing the substrate to a sputtering gas.

In some embodiments, the methods involve, after selectively depositingtungsten in the feature, non-selectively depositing tungsten in thefeature. Transitioning from selective to non-selective deposition mayinvolve allowing a CVD process to continue without deposition of anintervening tungsten nucleation layer. Transitioning from selective tonon-selective deposition may involve deposition of a tungsten nucleationlayer on the selectively deposited tungsten.

In some embodiments, selectively inhibiting tungsten nucleation includestreating a tungsten surface of the feature. In some embodiments,selectively inhibiting tungsten nucleation includes treating a metalnitride surface of the feature.

In some embodiments selective inhibition is performed without etchingmaterial in the feature. In some embodiments, feature fill is performedwithout etching material in the feature. The feature may be part of a3-D structure.

In some embodiments, the method includes repeating a cycle of selectiveinhibition and selective deposition one or more times to fill thefeature.

In some embodiments, selectively inhibiting tungsten nucleation in thefeature includes exposing the feature to a direct plasma while applyinga bias to the substrate. A direct plasma may include one or more ofnitrogen, hydrogen, oxygen and carbon activated species. In someembodiments, the plasma is nitrogen-based and/or hydrogen-based. In someembodiments, selectively inhibiting tungsten nucleation in the featureincludes exposing the feature to a remotely-generated plasma. In someembodiments, the method involves depositing a tungsten layer in thefeature prior to selective inhibition.

Examples of modulating the differential inhibition profile includesoaking the feature in a reducing agent or tungsten-containing agent,annealing the substrate, exposing the feature to a hydrogen-containingplasma, and exposing the substrate to a sputtering gas.

In some embodiments, the methods involve, after selectively depositingtungsten in the feature, non-selectively depositing tungsten in thefeature. Transitioning from selective to non-selective deposition mayinvolve allowing a CVD process to continue without deposition of anintervening tungsten nucleation layer. Transitioning from selective tonon-selective deposition may involve deposition of a tungsten nucleationlayer on the selectively deposited tungsten.

In some embodiments, selectively inhibiting tungsten nucleation includestreating a tungsten surface of the feature. In some embodiments,selectively inhibiting tungsten nucleation includes treating a metalnitride surface of the feature.

In some embodiments selective inhibition is performed without etchingmaterial in the feature. In some embodiments, feature fill is performedwithout etching material in the feature. The feature may be part of a3-D structure.

In some embodiments, the method includes repeating a cycle of selectiveinhibition and selective deposition one or more times to fill thefeature.

In some embodiments, selectively inhibiting tungsten nucleation in thefeature includes exposing the feature to a direct plasma while applyinga bias to the substrate. A direct plasma may include one or more ofnitrogen, hydrogen, oxygen and carbon activated species. In someembodiments, the plasma is nitrogen-based and/or hydrogen-based. In someembodiments, selectively inhibiting tungsten nucleation in the featureincludes exposing the feature to a remotely-generated plasma. In someembodiments, the method involves depositing a tungsten layer in thefeature prior to selective inhibition.

Examples of modulating the differential inhibition profile includesoaking the feature in a reducing agent or tungsten-containing agent,annealing the substrate, exposing the feature to a hydrogen-containingplasma, and exposing the substrate to a sputtering gas.

In some embodiments, the methods involve, after selectively depositingtungsten in the feature, non-selectively depositing tungsten in thefeature. Transitioning from selective to non-selective deposition mayinvolve allowing a CVD process to continue without deposition of anintervening tungsten nucleation layer. Transitioning from selective tonon-selective deposition may involve deposition of a tungsten nucleationlayer on the selectively deposited tungsten.

In some embodiments, selectively inhibiting tungsten nucleation includestreating a tungsten surface of the feature. In some embodiments,selectively inhibiting tungsten nucleation includes treating a metalnitride surface of the feature.

In some embodiments selective inhibition is performed without etchingmaterial in the feature. In some embodiments, feature fill is performedwithout etching material in the feature. The feature may be part of a3-D structure.

In some embodiments, the method includes repeating a cycle of selectiveinhibition and selective deposition one or more times to fill thefeature.

In some embodiments, selectively inhibiting tungsten nucleation in thefeature includes exposing the feature to a direct plasma while applyinga bias to the substrate. A direct plasma may include one or more ofnitrogen, hydrogen, oxygen and carbon activated species. In someembodiments, the plasma is nitrogen-based and/or hydrogen-based. In someembodiments, selectively inhibiting tungsten nucleation in the featureincludes exposing the feature to a remotely-generated plasma. In someembodiments, the method involves depositing a tungsten layer in thefeature prior to selective inhibition.

Examples of modulating the differential inhibition profile includesoaking the feature in a reducing agent or tungsten-containing agent,annealing the substrate, exposing the feature to a hydrogen-containingplasma, and exposing the substrate to a sputtering gas.

In some embodiments, the methods involve, after selectively depositingtungsten in the feature, non-selectively depositing tungsten in thefeature. Transitioning from selective to non-selective deposition mayinvolve allowing a CVD process to continue without deposition of anintervening tungsten nucleation layer. Transitioning from selective tonon-selective deposition may involve deposition of a tungsten nucleationlayer on the selectively deposited tungsten.

In some embodiments, selectively inhibiting tungsten nucleation includestreating a tungsten surface of the feature. In some embodiments,selectively inhibiting tungsten nucleation includes treating a metalnitride surface of the feature.

In some embodiments selective inhibition is performed without etchingmaterial in the feature. In some embodiments, feature fill is performedwithout etching material in the feature. The feature may be part of a3-D structure.

In some embodiments, the method includes repeating a cycle of selectiveinhibition and selective deposition one or more times to fill thefeature.

Another aspect involves a method including providing a substrateincluding a feature having one or more feature openings and a featureinterior; exposing the feature to one of: an oxidizing environment, avacuum break, a reducing agent soak, or a tungsten-containing agentsoak; after exposing the feature, selectively inhibiting tungstennucleation in the feature such that there is a differential inhibitionprofile along a feature axis; and selectively depositing tungsten in thefeature in accordance with the modified differential inhibition profile.

In some embodiments, selectively inhibiting tungsten nucleation in thefeature includes exposing the feature to a direct plasma while applyinga bias to the substrate. The plasma may contains one or more ofnitrogen, hydrogen, oxygen and carbon activated species.

The plasma may be nitrogen-based or hydrogen-based in some embodiments.

In some embodiments, selectively inhibiting tungsten nucleation in thefeature includes exposing the feature to a remotely-generated plasma.The method may further involve depositing a tungsten layer in thefeature prior to selective inhibition.

In some embodiments, exposing the feature includes soaking the featurein a reducing agent or tungsten-containing agent.

In some embodiments, the method involves modulating the differentialinhibition profile.

In some embodiments, the method involves, after selectively depositingtungsten in the feature, depositing tungsten in the feature to completefeature fill.

In some embodiments, the method involves, after selectively depositingtungsten in the feature, non-selectively depositing tungsten in thefeature. Transitioning from selective to non-selective deposition mayinvolve allowing a CVD process to continue without deposition of anintervening tungsten nucleation layer. Transitioning from selective tonon-selective deposition may involve deposition of a tungsten nucleationlayer on the selectively deposited tungsten.

In some embodiments, selectively inhibiting tungsten nucleation includestreating a tungsten surface of the feature. In some embodiments,selectively inhibiting tungsten nucleation includes treating a metalnitride surface of the feature.

In some embodiments selective inhibition is performed without etchingmaterial in the feature. In some embodiments, feature fill is performedwithout etching material in the feature. The feature may be part of a3-D structure.

Another aspect is a method involving, prior to processing a one or moresubstrates in a tungsten deposition chamber, exposing the tungstendeposition chamber to an inhibition treatment.

Another aspect is an apparatus including one or more chambers configuredto support a substrate; an in situ plasma generator configured togenerate a plasma in one or more of the chambers; gas inlets configuredto direct gas into each of the one or more chambers; and a controllerincluding program instructions for performing any of the methods above.

These and other aspects are described further below with reference tothe drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A-1G show examples of various structures that can be filledaccording to the processes described herein.

FIGS. 2A-2C are process flow diagrams illustrating certain operations inmethods of filling features with tungsten.

FIG. 2D is a graph showing growth delay time (after inhibition) as afunction of thickness of tungsten layer deposited prior to theinhibition treatment.

FIGS. 3A-3C, 4A-4D and 4F-4H are process flow diagrams illustratingcertain operations in methods of selective inhibition.

FIG. 3D is a graph showing inhibition modulation as function ofpre-inhibition exposure to air duration.

FIG. 4E is a graph showing inhibition modulation as a function ofpost-inhibition anneal duration.

FIG. 4I is a bar graph showing the effect of a post-inhibition hydrogenplasma on inhibition.

FIGS. 5-7 are schematic diagrams showing features at various stages offeature fill.

FIGS. 8, 9A and 9B are schematic diagrams showing examples of apparatussuitable for practicing the methods described herein.

FIG. 10 shows a process diagram illustrating operations in a method ofcleaning a deposition chamber.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Thepresent invention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail to not unnecessarily obscure the present invention.While the invention will be described in conjunction with the specificembodiments, it will be understood that it is not intended to limit theinvention to the embodiments.

Described herein are methods of filling features with tungsten (W) andrelated systems and apparatus. Examples of application include logic andmemory contact fill, DRAM buried wordline fill, vertically integratedmemory gate/wordline fill, and 3-D integration with through-silicon vias(TSVs). The methods described herein can be used to fill verticalfeatures, such as in tungsten vias, and horizontal features, such asvertical NAND (VNAND) wordlines. The methods may be used for conformaland bottom-up or inside-out fill.

According to various embodiments, a features can be characterized by oneor more of narrow and/or re-entrant openings, constrictions within thefeatures, and high aspect ratios. Examples of features that can befilled are depicted in FIGS. 1A-1C. FIG. 1A shows an example of across-sectional depiction of a vertical feature 101 to be filled withtungsten. The feature can include a feature hole 105 in a substrate 103.The substrate may be a silicon wafer, e.g., 200-mm wafer, 300-mm wafer,or 450-mm wafer, including wafers having one or more layers of materialsuch as dielectric, conducting, or semi-conducting material depositedthereon. In some embodiments, the feature hole 105 may have an aspectratio of at least about 2:1, at least about 4:1, at least about 6:1 orhigher. The feature hole 105 may also have a dimension near the opening,e.g., an opening diameter or line width, of between about 10 nm to 500nm. For example, the opening dimension may be between about 25 nm to 300nm. The feature hole 105 may be referred to as an unfilled feature orsimply a feature. The feature, and any feature, may be characterized inpart by an axis 118 that extends through the length of the feature, withvertically-oriented features having vertical axes andhorizontally-oriented features having horizontal axes.

FIG. 1B shows an example of a feature 101 that has a re-entrant profile.A re-entrant profile is a profile that narrows from a closed bottom endto the feature opening or from an interior of the feature to the featureopening. According to various embodiments, the profile may narrowgradually and/or include an overhang at the feature opening. FIG. 1Bshows an example of the latter, with an underlayer 113 lining theinterior surfaces of the feature hole 105. The underlayer 113 can be forexample, a diffusion barrier layer, an adhesion layer, a nucleationlayer, a combination of thereof, or any other appropriate material.Examples of such underlayers include titanium nitride (TiN) underlayers,titanium/titanium nitride (Ti/TiN) underlayers, and tungsten nitride(WN) underlayers. The underlayer 113 forms an overhang 115 such that theunderlayer 113 is thicker near the opening of the feature 101 thaninside the feature 101.

In some embodiments, features having one or more constrictions withinthe feature may be filled. FIG. 1C shows examples of views of variousfilled features having constrictions. Each of the examples (a), (b) and(c) in FIG. 1C includes a constriction 109 at a midpoint of the feature.The constriction 109 can be, for example, between about 15 nm to 20 nmwide. Constrictions can cause pinch off during deposition of tungsten inthe feature using conventional techniques, with deposited tungstenblocking further deposition past the constriction before that portion ofthe feature is filled, resulting in voids in the feature. Example (b)further includes a liner/barrier overhang 115 at the feature opening.Such an overhang could also be a potential pinch-off point. Example (c)includes a constriction 112 further away from the field region than theoverhang 115 in example (b). As described further below, methodsdescribed herein allow void-free fill as depicted in FIG. 1C.

Horizontal features, such as in 3-D memory structures, can also befilled. FIG. 1D shows an example of a word line 150 in a VNAND structure148 that includes a constriction 151. In some embodiments, theconstrictions can be due to the presence of pillars in a VNAND or otherstructure. FIG. 1E, for example, shows a plan view of pillars 125 in aVNAND structure, with FIG. 1F showing a simplified schematic of across-sectional depiction of the pillars 125. Arrows in FIG. 1Erepresent deposition material; as pillars 125 are disposed between anarea 127 and a gas inlet or other deposition source, adjacent pillarscan result in constrictions that present challenges in void free fill ofthe area 127.

FIG. 1G provides another example of a view horizontal feature, forexample, of a VNAND or other structure including pillar constrictions151. The example in FIG. 1G is open-ended, with material to be depositedable to enter laterally from two sides as indicated by the arrows. (Itshould be noted that example in FIG. 1G can be seen as a 2-D rendering3-D features of the structure, with the FIG. 1G being a cross-sectionaldepiction of an area to be filled and pillar constrictions shown in thefigure representing constrictions that would be seen in a plan ratherthan cross-sectional view.) In some embodiments, 3-D structures can becharacterized with the area to be filled extending along threedimensions (e.g., in the X, Y and Z-directions in the example of FIG.1F), and can present more challenges for fill than filling holes ortrenches that extend along one or two dimensions. For example,controlling fill of a 3-D structure can be challenging as depositiongasses may enter a feature from multiple dimensions.

Filling features with tungsten-containing materials may cause formationof voids and seams inside the filled features. A void is region in thefeature that is left unfilled. A void can form, for example, when thedeposited material forms a pinch point within the feature, sealing offan unfilled space within the feature preventing reactant entry anddeposition.

There are multiple potential causes for void and seam formation. One isan overhang formed near the feature opening during deposition oftungsten-containing materials or, more typically, other materials, suchas a diffusion barrier layer or a nucleation layer. An example of anoverhang is shown in FIG. 1B.

Another cause of void or seam formation that is not illustrated in FIG.1B but that nevertheless may lead to seam formation or enlarging seamsis curved sidewalls of feature holes. Features having such curvedsidewalls are also referred to as bowed features. In a bowed feature,the cross-sectional dimension of the cavity near the opening is smallerthan that inside the feature. Deposition challenges caused by thenarrowed openings of bowed features are similar to those caused byoverhangs as described above. Constrictions within a feature such asshown in FIGS. 1C, 1D and 1G also present challenges for tungsten fillwith few or no voids and seams.

Even if void free fill is achieved, tungsten in the feature may containa seam running through the axis or middle of the via, trench, line orother feature. This is because tungsten growth can begin at the sidewalland continue until the tungsten grains meet with tungsten growing fromthe opposite sidewall. This seam can allow for trapping of impuritiesincluding fluorine-containing compounds such as hydrofluoric acid (HF).During chemical-mechanical planarization (CMP), coring can alsopropagate from the seam. According to various embodiments, the methodsdescribed herein can reduce or eliminate void and seam formation. Themethods described herein may also address one or more of the following:

1) Very challenging profiles: Void free fill can be achieved in mostre-entrant features using deposition-etch-deposition (dep-etch-dep)cycles as described in U.S. Pat. No. 8,435,894, incorporated byreference herein. However, depending on the dimensions and geometry,multiple dep-etch-dep cycles may be needed to achieve void-free fill.This can affect process stability and throughput. Embodiments describedherein can provide feature fill with fewer or no dep-etch-dep cycles.

2) Small features and liner/barrier impact: In cases where the featuresizes are extremely small, tuning the etch process without impacting theintegrity of a liner/barrier underlayer can be very difficult. In somecases intermittent titanium (Ti) attack can occur during a W-selectiveetch. This may be due to formation of a passivating titanium fluoride(TiF_(x)) layer during the etch.

3) Scattering at W grain boundaries: The presence of multiple W grainsinside the feature can result in electron loss due to grain boundaryscattering. As a result, actual device performance will be degradedcompared to theoretical predictions and blanket wafer results.

4) Reduced via volume for W fill: Especially in smaller and newerfeatures, a significant part of the metal contact is used up by the Wbarrier (e.g., a TiN or WN, etc. barrier). These films are typicallyhigher resistivity than W and negatively impact electricalcharacteristics like contact resistance.

FIG. 2A is a process flow diagram illustrating certain operations in amethod of filling a feature with tungsten. The method begins at a block201 with selective inhibition of a feature. Selective inhibition, whichmay also be referred to as preferential inhibition, preferentialpassivation, selective passivation, differential inhibition, ordifferential passivation, involves inhibiting subsequent tungstennucleation on a portion of the feature, while not inhibiting nucleation(or inhibiting nucleation to a lesser extent) on the remainder of thefeature. For example, in some embodiments, a feature is selectivelyinhibited at a feature opening, while nucleation inside the feature isnot inhibited. Selective inhibition is described further below, and caninvolve, for example, selectively exposing a portion of the feature toactivated species of a plasma. In certain embodiments, for example, afeature opening is selectively exposed to a plasma generated frommolecular nitrogen gas. As discussed further below, a desired inhibitionprofile in a feature can be formed by appropriately selecting one ormore of inhibition chemistry, substrate bias power, plasma power,process pressure, exposure time, and other process parameters.

Once the feature is selectively inhibited, the method can continue atblock 203 with selective deposition of tungsten according to theinhibition profile. Block 203 may involve one or more chemical vapordeposition (CVD) and/or atomic layer deposition (ALD) processes,including thermal and plasma-enhanced CVD and/or ALD processes. Thedeposition is selective in that the tungsten preferentially grows on thelesser- and non-inhibited portions of the feature. In some embodiments,block 203 involves selectively depositing tungsten in a bottom orinterior portion of the feature until a constriction is reached orpassed.

After selective deposition according to the inhibition profile isperformed, the method can continue at block 205 with filling the rest ofthe feature. In certain embodiments, block 205 involves a CVD process inwhich a tungsten-containing precursor is reduced by hydrogen to deposittungsten. While tungsten hexafluoride (WF₆) is often used, the processmay be performed with other tungsten precursors, including, but notlimited to, tungsten hexachloride (WCl₆), organo-metallic precursors,and precursors that are free of fluorine such as MDNOW(methylcyclopentadienyl-dicarbonylnitrosyl-tungsten) and EDNOW(ethylcyclopentadienyl-dicarbonylnitrosyl-tungsten). In addition, whilehydrogen can be used as the reducing agent in the CVD deposition, otherreducing agents including silane may be used in addition or instead ofhydrogen. In another embodiment, tungsten hexacarbonyl (W(CO)₆) may beused with or without a reducing agent. Unlike with ALD and pulsednucleation layer (PNL) processes described further below, in a CVDtechnique, the WF₆ and H₂ or other reactants are simultaneouslyintroduced into the reaction chamber. This produces a continuouschemical reaction of mix reactant gases that continuously forms tungstenfilm on the substrate surface. Methods of depositing tungsten filmsusing CVD are described in U.S. Pat. Nos. 8,551,885 and 8,623,733, whichare incorporated by reference herein in their entireties for thepurposes of describing tungsten deposition processes. According tovarious embodiments, the methods described herein are not limited to aparticular method of filling a feature but may include any appropriatedeposition technique.

In some embodiments, block 205 may involve continuing a CVD depositionprocess started at block 203. Such a CVD process may result indeposition on the inhibited portions of the feature, with nucleationoccurring more slowly than on the non-inhibited portions of the feature.In some embodiments, block 205 may involve deposition of a tungstennucleation layer over at least the inhibited portions of the feature.

According to various embodiments, the feature surface that isselectively inhibited can be a barrier or liner layer, such as a metalnitride layer, or it can be a layer deposited to promote nucleation oftungsten. FIG. 2B shows an example of a method in which a tungstennucleation layer is deposited in the feature prior to selectiveinhibition. The method begins at block 301 with deposition of the thinconformal layer of tungsten in the feature. The layer can facilitatesubsequent deposition of bulk tungsten-containing material thereon. Incertain embodiments, the nucleation layer is deposited using a PNLtechnique. In a PNL technique, pulses of a reducing agent, purge gases,and tungsten-containing precursor can be sequentially injected into andpurged from the reaction chamber. The process is repeated in a cyclicalfashion until the desired thickness is achieved. PNL broadly embodiesany cyclical process of sequentially adding reactants for reaction on asemiconductor substrate, including ALD techniques. PNL techniques fordepositing tungsten nucleation layers are described in U.S. Pat. Nos.6,635,965; 7,589,017; 7,141,494; 7,772,114; 8,058,170 and 8,623,733 andin U.S. patent application Ser. No. 12/755,248, which are incorporatedby reference herein in their entireties for the purposes of describingtungsten deposition processes. Block 301 is not limited to a particularmethod of tungsten nucleation layer deposition, but includes PNL, ALD,CVD, and physical vapor deposition (PVD) techniques for depositing athin conformal layer. The nucleation layer can be sufficiently thick tofully cover the feature to support high quality bulk deposition;however, because the resistivity of the nucleation layer is higher thanthat of the bulk layer, the thickness of the nucleation layer may beminimized to keep the total resistance as low as possible. Examplethicknesses of films deposited in block 301 can range from less than 10Å to 100 Å. After deposition of the thin conformal layer of tungsten inblock 301, the method can continue with blocks 201, 203, and 205 asdescribed above with reference to FIG. 2A. An example of filling afeature according to a method of FIG. 2B is described below withreference to FIG. 5.

In some embodiments, the thickness of the layer deposited in block 301may be used to modulate the inhibition effect of the subsequentoperation. FIG. 2D shows growth delay time (after inhibition) as afunction of thickness of tungsten layer deposited prior to theinhibition treatment. The thinner the layer, the stronger the inhibitingeffect.

FIG. 2C shows an example of a method in which completing filling thefeature (e.g., block 205 in FIG. 2A) can involve repeating selectiveinhibition and deposition operations. The method can begin at block 201,as described above with respect to FIG. 2A, in which the feature isselectively inhibited, and continue at block 203 with selectivedeposition according to the inhibition profile. Blocks 201 and 203 arethen repeated one or more times (block 401) to complete feature fill.

Still further, selective inhibition can be used in conjunction withselective deposition. Selective deposition techniques are described inU.S. Provisional Patent Application No. 61/616,377, incorporated byreference herein.

According to various embodiments, selective inhibition can involveexposure to activated species that passivate the feature surfaces. Forexample, in certain embodiments, a tungsten surface can be passivated byexposure to a nitrogen-based or hydrogen-based plasma. In someembodiments, inhibition can involve a chemical reaction betweenactivated species and the feature surface to form a thin layer of acompound material such as tungsten nitride (WN) or tungsten carbide(WC). In some embodiments, inhibition can involve a surface effect suchas adsorption that passivates the surface without forming a layer of acompound material. Activated species may be formed by any appropriatemethod including by plasma generation and/or exposure to ultraviolet(UV) radiation. In some embodiments, the substrate including the featureis exposed to a plasma generated from one or more gases fed into thechamber in which the substrate sits. In some embodiments, one or moregases may be fed into a remote plasma generator, with activated speciesformed in the remote plasma generator fed into a chamber in which thesubstrate sits. The plasma source can be any type of source includingradio frequency (RF) plasma source or microwave source. The plasma canbe inductively and/or capacitively-coupled. Activated species caninclude atomic species, radical species, and ionic species. In certainembodiments, exposure to a remotely-generated plasma includes exposureto radical and atomized species, with substantially no ionic speciespresent in the plasma such that the inhibition process is notion-mediated. In other embodiments, ion species may be present in aremotely-generated plasma. In certain embodiments, exposure to anin-situ plasma involves ion-mediated inhibition. For the purposes ofthis application, activated species are distinguished from recombinedspecies and from the gases initially fed into a plasma generator.

Inhibition chemistries can be tailored to the surface that will besubsequently exposed to deposition gases. For tungsten surfaces, asformed for example in a method described with reference to FIG. 2B,exposure to nitrogen-based and/or hydrogen-based plasmas inhibitssubsequent tungsten deposition on the W surfaces. Other chemistries thatmay be used for inhibition of tungsten surfaces include oxygen-basedplasmas and hydrocarbon-based plasmas. For example, molecular oxygen ormethane may be introduced to a plasma generator.

As used herein, a nitrogen-based plasma is a plasma in which the mainnon-inert component is nitrogen. An inert component such as argon,xenon, or krypton may be used as a carrier gas. In some embodiments, noother non-inert components are present in the gas from which the plasmais generated except in trace amounts. In some embodiments, inhibitionchemistries may be nitrogen-containing, hydrogen-containing,oxygen-containing, and/or carbon-containing, with one or more additionalreactive species present in the plasma. For example, U.S. Pat. No.8,124,531, incorporated by reference herein, describes passivation of atungsten surface by exposure to nitrogen trifluoride (NF₃). Similarly,fluorocarbons such as CF₄ or C₂F₈ may be used. However, in certainembodiments, the inhibition species are fluorine-free to prevent etchingduring selective inhibition.

In certain embodiments, UV radiation may be used in addition to orinstead of plasma to provide activated species. Gases may be exposed toUV light upstream of and/or inside a reaction chamber in which thesubstrate sits. Moreover, in certain embodiments, non-plasma, non-UV,thermal inhibition processes may be used. In addition to tungstensurfaces, nucleation may be inhibited on liner/barrier layers surfacessuch as TiN and/or WN surfaces. Any chemistry that passivates thesesurfaces may be used. For TiN and WN, this can include exposure tonitrogen-based or nitrogen-containing chemistries. In certainembodiments, the chemistries described above for W may also be employedfor TiN, WN, or other liner layer surfaces.

Tuning an inhibition profile can involve appropriately controlling aninhibition chemistry, substrate bias power, plasma power, processpressure, exposure time, and other process parameters. For in-situplasma processes (or other processes in which ionic species arepresent), a bias can be applied to the substrate. Substrate bias can, insome embodiments, significantly affect an inhibition profile, withincreasing bias power resulting in active species deeper within thefeature. For example, 100 W DC bias on a 300 mm substrate may resultinhibition the top half of a 1500 nm deep structure, while a 700 W biasmay result in inhibition of the entire structure. The absolute biaspower appropriate a particular selective inhibition will depend on thesubstrate size, the system, plasma type, and other process parameters,as well as the desired inhibition profile; however, bias power can beused to tune top-to-bottom selectivity, with decreasing bias powerresulting in higher selectivity. For 3-D structures in which selectivityis desired in a lateral direction (tungsten deposition preferred in theinterior of the structure), but not in a vertical direction, increasedbias power can be used to promote top-to-bottom deposition uniformity.

While bias power can be used in certain embodiments as the primary oronly knob to tune an inhibition profile for ionic species, in certainsituations, performing selective inhibition uses other parameters inaddition to or instead of bias power. These include remotely generatednon-ionic plasma processes and non-plasma processes. Also, in manysystems, a substrate bias can be easily applied to tune selectivity invertical but not lateral direction. Accordingly, for 3-D structures inwhich lateral selectivity is desired, parameters other than bias may becontrolled, as described above.

Inhibition chemistry can also be used to tune an inhibition profile,with different ratios of active inhibiting species used. For example,for inhibition of W surfaces, nitrogen may have a stronger inhibitingeffect than hydrogen; adjusting the ratio of N₂ and H₂ gas in a forminggas-based plasma can be used to tune a profile. The plasma power mayalso be used to tune an inhibition profile, with different ratios ofactive species tuned by plasma power. Process pressure can be used totune a profile, as pressure can cause more recombination (deactivatingactive species) as well as pushing active species further into afeature. Process time may also be used to tune inhibition profiles, withincreasing treatment time causing inhibition deeper into a feature.

In some embodiments, selective inhibition can be achieved by performingoperation 203 in a mass transport limited regime. In this regime, theinhibition rate inside the feature is limited by amounts of and/orrelative compositions of different inhibition material components (e.g.,an initial inhibition species, activated inhibition species, andrecombined inhibition species) that diffuse into the feature. In certainexamples, inhibition rates depend on various components' concentrationsat different locations inside the feature.

Mass transport limiting conditions may be characterized, in part, byoverall inhibition concentration variations. In certain embodiments, aconcentration is less inside the feature than near its opening resultingin a higher inhibition rate near the opening than inside. This in turnleads to selective inhibition near the feature opening. Mass transportlimiting process conditions may be achieved by supplying limited amountsof inhibition species into the processing chamber (e.g., use lowinhibition gas flow rates relative to the cavity profile anddimensions), while maintaining relative high inhibition rates near thefeature opening to consume some activated species as they diffuse intothe feature. In certain embodiment, a concentration gradient issubstantial, which may be caused relatively high inhibition kinetics andrelatively low inhibition supply. In certain embodiments, an inhibitionrate near the opening may also be mass transport limited, though thiscondition is not required to achieve selective inhibition.

In addition to the overall inhibition concentration variations insidefeatures, selective inhibition may be influenced by relativeconcentrations of different inhibition species throughout the feature.These relative concentrations in turn can depend on relative dynamics ofdissociation and recombination processes of the inhibition species. Asdescribed above, an initial inhibition material, such as molecularnitrogen, can be passed through a remote plasma generator and/orsubjected to an in-situ plasma to generate activated species (e.g.,atomic nitrogen, nitrogen ions). However, activated species mayrecombine into less active recombined species (e.g., nitrogen molecules)and/or react with W, WN, TiN, or other feature surfaces along theirdiffusion paths. As such, different parts of the feature may be exposedto different concentrations of different inhibition materials, e.g., aninitial inhibition gas, activated inhibition species, and recombinedinhibition species. This provides additional opportunities forcontrolling selective inhibition. For example, activated species aregenerally more reactive than initial inhibition gases and recombinedinhibition species. Furthermore, in some cases, the activated speciesmay be less sensitive to temperature variations than the recombinedspecies. Therefore, process conditions may be controlled in such a waythat removal is predominantly attributed to activated species. As notedabove, some species may be more reactive than others. Furthermore,specific process conditions may result in activated species beingpresent at higher concentrations near features' openings than inside thefeatures. For example, some activated species may be consumed (e.g.,reacted with feature surface materials and/or adsorbed on the surface)and/or recombined while diffusing deeper into the features, especiallyin small high aspect ratio features. Recombination of activated speciescan also occur outside of features, e.g., in the showerhead or theprocessing chamber, and can depends on chamber pressure. Therefore,chamber pressure may be controlled to adjust concentrations of activatedspecies at various points of the chamber and features.

Flow rates of the inhibition gas can depend on a size of the chamber,reaction rates, and other parameters. A flow rate can be selected insuch a way that more inhibition material is concentrated near theopening than inside the feature. In certain embodiments, these flowrates cause mass-transport limited selective inhibition. For example, aflow rate for a 195-liter chamber per station may be between about 25sccm and 10,000 sccm or, in specific embodiments, between about 50 sccmand 1,000 sccm. In certain embodiments, the flow rate is less than about2,000 sccm, less than about 1,000 sccm, or more less than about 500sccm. It should be noted that these values are presented for oneindividual station configured for processing a 300-mm substrate. Theseflow rates can be scaled up or down depending on a substrate size, anumber of stations in the apparatus (e.g., quadruple for a four stationapparatus), a processing chamber volume, and other factors.

In certain embodiments, the substrate can be heated up or cooled downbefore selective inhibition. Various devices may be used to bring thesubstrate to the predetermined temperature, such as a heating or coolingelement in a station (e.g., an electrical resistance heater installed ina pedestal or a heat transfer fluid circulated through a pedestal),infrared lamps above the substrate, igniting plasma, etc.

A predetermined temperature for the substrate can be selected to inducea chemical reaction between the feature surface and inhibition speciesand/or promote adsorption of the inhibition species, as well as tocontrol the rate of the reaction or adsorption. For example, atemperature may be selected to have high reaction rate such that moreinhibition occurs near the opening than inside the feature. Furthermore,a temperature may be also selected to control recombination of activatedspecies (e.g., recombination of atomic nitrogen into molecular nitrogen)and/or control which species (e.g., activated or recombined species)contribute predominantly to inhibition. In certain embodiments, asubstrate is maintained at less than about 300° C., or more particularlyat less than about 250° C., or less than about 150° C., or even lessthan about 100° C. In other embodiments, a substrate is heated tobetween about 300° C. and 450° C. or, in more specific embodiments, tobetween about 350° C. and 400° C. Other temperature ranges may be usedfor different types of inhibition chemistries. Exposure time can also beselected to cause selective inhibition. Example exposure times can rangefrom about 10 s to 500 s, depending on desired selectivity and featuredepth.

In some embodiments, the inhibition treatments described above aremodulated to improve selectivity and tune the inhibition profile. FIGS.3A-3C and 4A-4D provide examples of flow charts of selectivelyinhibiting tungsten deposition in a feature. FIGS. 3A-3C provideexamples of treating a substrate prior to exposing the substrate to annitrogen-based plasma or other inhibition chemistry. First, in FIG. 3A,the process begins by exposing a substrate including a feature to acontrolled vacuum break (350). As used herein, a vacuum break refers toa period wherein the substrate is not under vacuum. In block 350, thesubstrate may be exposed to atmospheric pressure, for example, in astorage cassette (e.g., a front opening unified pod or FOUP) or in aloadlock. In some embodiments, the substrate may be exposed toatmospheric temperature and/or gasses (i.e., air). Alternatively,temperature and gas composition may be controlled. The duration of block350 may be controlled to effectively modulate the subsequent inhibitiontreatment. Next, the substrate is exposed to an inhibition treatment asdiscussed above (352). In a particular example, the substrate is exposedto a nitrogen-based plasma. The process shown in FIG. 3A may beperformed as part of block 201 in a process as shown in FIGS. 2A-2C. Insome embodiments, block 350 is performed after deposition of a thin filmin the feature, for example as shown in block 301 of FIG. 2A. In oneexample, a thin tungsten film may be deposited in a feature in a firstvacuum chamber, followed by a controlled vacuum break in a FOUP orloadlock, followed by exposure to a nitrogen-based plasma in a secondvacuum chamber.

The process of FIG. 3B is similar to that of FIG. 3A, with a substrateincluding a feature exposed to an oxidizing chemistry (354). In someembodiments, block 354 may be performed outside a reaction chamber, forexample in a FOUP or loadlock. Alternatively, block 354 may involveexposing a substrate to an oxidizing gas, such as oxygen (O₂), ozone(O₃), carbon dioxide (CO₂), water (H₂O), etc. in a process chamber.Block 354 may be performed under vacuum or at atmospheric pressure.According to various embodiments, block 354 may or may not involve theuse of plasma- or UV-activated species. For example, block 354 mayinvolve exposing the substrate to O₂ under non-plasma conditions suchthat the O₂ is not activated. Block 354 is followed by exposing thesubstrate to an inhibition treatment (352). In a particular example, thesubstrate is exposed to a nitrogen-based plasma. Blocks 354 and 352 maybe performed in the same chamber or different chambers. The processshown in FIG. 3B may be performed as part of block 201 in a process asshown in FIGS. 2A-2C. In some embodiments, block 354 is performed afterdeposition of a thin film in the feature, for example as shown in block301 of FIG. 2B.

In some embodiments, block 350 in FIG. 3A or block 354 in FIG. 3B ininvolves formation of an oxide film in the feature. For example, inimplementations in which there is a thin conformal tungsten filmdeposited in the feature (e.g., as in block 301 of FIG. 2B), tungstenoxide (WO_(x)) may be formed in the feature. In some embodiments, WO_(x)formation in a feature is non-conformal.

FIG. 3D shows growth delay of a tungsten deposition performed after thefollowing sequence: a) deposition of tungsten layer, b) exposure to air(vacuum break) and c) exposure to a nitrogen-based plasma inhibitingtreatment. The delay time is shown as a function of the air exposuretime. As shown in FIG. 3D, an air break modulates the inhibition effectof the nitrogen plasma by lessening the effect.

The process of FIG. 3C involves exposing a substrate including a featureto a reactive chemistry (356). Examples of reactive chemistries includereducing chemistries (e.g., diborane (B₂H₆) or silane (SiH₄)) andtungsten-containing chemistries (e.g., WF₆ or WCl₆). Block 356 isfollowed by exposing the substrate to an inhibition treatment (352). Ina particular example, the substrate is exposed to a nitrogen-basedplasma. Blocks 356 and 352 may be performed in the same chamber ordifferent chambers. The process shown in FIG. 3C may be performed aspart of block 201 in a process as shown in FIGS. 2A-2C. In someembodiments, block 356 is performed after deposition of a thin film inthe feature, for example as shown in block 301 of FIG. 2B. Block 356 maybe referred to as a soak, and is generally a non-plasma operation.

Table 1, below, compares inhibition performed after a diborane soak withinhibition performed after no soak. For both processes, a 100 Å tungstennucleation layer was deposited, followed by the soak/no soak operation,followed by exposure to a nitrogen plasma. The deposition operationfollowing the inhibition treatment was 300 seconds (including delay).

Pre-inhibition 300 second 300 second B₂H₆ soaking W deposition: Wdeposition: (seconds) thickness (Å) delay (seconds) 0 897 221 15100 >300 sThe results in Table 1 indicate that the B₂H₆ rich surface modulates theinhibition effect by increasing it.

FIGS. 4A-4D provide examples of treating a substrate after exposing thesubstrate to an nitrogen-based plasma or other inhibition chemistry andprior to tungsten deposition. The treatment modulates the inhibition.First, in FIG. 4A, the process includes exposing a substrate including afeature to an inhibition treatment as discussed above (450). In aparticular example, the substrate is exposed to a nitrogen-based plasma.Next, the substrate is annealed (452). Block 452 may involve raising thetemperature, e.g., by at least 50° C., 100° C. or 200° C. The annealingmay be performed in an inert ambient, or in an oxidizing environment,for example. Blocks 450 and 452 may be performed in the same chamber ordifferent chambers. The process shown in FIG. 4A may be performed aspart of block 201 in a process as shown in FIGS. 2A-2C. Block 452 may beperformed in a chamber where a subsequent tungsten deposition operationis to be performed. In some embodiments, block 450 may be performed aspart of block 352 in FIGS. 3A-3C, i.e., after a modulation pretreatment.Block 450 may form a differential inhibition profile along a featureaxis, with block 452 forming a modified differential inhibition profilealong the feature axis.

The process of FIG. 4B involves exposing a substrate including a featureto a reactive chemistry (454) after exposing it to an inhibitiontreatment (450) as described above. Examples of reactive chemistriesinclude reducing chemistries (e.g., B₂H₆, SiH₄) and tungsten-containingchemistries (e.g., WF₆, WCl₆). Blocks 450 and 454 may be performed inthe same chamber or different chambers. The process shown in FIG. 4B maybe performed as part of block 201 in a process as shown in FIGS. 2A-2C.In some embodiments, the reactive chemistry in block 454 is one or morecompounds used in a subsequent tungsten deposition operation. In someembodiments, block 450 may be performed as part of block 352 in FIGS.3A-3C, i.e., after a modulation pretreatment. Block 454 may be referredto as a soak, and is generally a non-plasma operation. Block 450 mayform a differential inhibition profile along a feature axis, with block454 forming a modified differential inhibition profile along the featureaxis.

The process of FIG. 4C involves exposing a substrate including a featureto an oxidizing chemistry (456) after exposing it to an inhibitiontreatment (450) as described above. Examples of oxidizing chemistriesinclude O₂, O₃, CO₂, and H₂O. Block 456 may be performed at the same ordifferent temperature than block 450. According to various embodiments,block 456 may or may not involve the use of plasma- or UV-activatedspecies. For example, block 456 may involve exposing the substrate to O₂under non-plasma conditions such that the O₂ is not activated. Blocks450 and 456 may be performed in the same chamber or different chambers.The process shown in FIG. 4C may be performed as part of block 201 in aprocess as shown in FIGS. 2A-2C. In some embodiments, block 450 may beperformed as part of block 352 in FIGS. 3A-3C, i.e., after a modulationpretreatment. Block 450 may form a differential inhibition profile alonga feature axis, with block 456 forming a modified differentialinhibition profile along the feature axis.

The process of FIG. 4D involves exposing a substrate including a featureto a sputtering gas (458) after exposing it to an inhibition treatment(450) as described above. Examples of sputtering gases include Ar andH₂. Blocks 450 and 458 may be performed in the same chamber or differentchambers. The process shown in FIG. 4D may be performed as part of block201 in a process as shown in FIGS. 2A-2C. In some embodiments, block 450may be performed as part of block 352 in FIGS. 3A-3C, i.e., after amodulation pretreatment. Block 450 may form a differential inhibitionprofile along a feature axis, with block 458 forming a modifieddifferential inhibition profile along the feature axis.

FIG. 4E shows growth delay of a tungsten deposition performed after thefollowing sequence: a) deposition of a tungsten layer, b) exposure to anitrogen-based plasma inhibiting treatment, and c) exposure to a thermalanneal. As shown in FIG. 4E, annealing modulates the inhibition effectof the nitrogen plasma by lessening the effect.

Table 2, below, compares inhibition prior to a diborane soak withinhibition performed prior to no soak. For both processes, a tungstenlayer was deposited, followed by exposure to a nitrogen plasma, followedby a soak/no soak operation.

Post-inhibition B₂H₆ W deposition W growth soaking (seconds) thickness(Å) delay (seconds) 0 564 1044 3 3187 170The results in Table 2 indicate that the post-inhibition B₂H₆ soakingmodulates the inhibition effect by decreasing it. This may be becausethe soaking with a reactive gas increases the nucleation sites.

The process of FIG. 4F involves exposing a substrate including a featureto an H-containing plasma (460) after exposing it to an inhibitiontreatment (450) as described above. Examples of H-containing plasmasinclude remote and in situ plasmas generated from hydrogen (H₂) gas.Blocks 450 and 460 may be performed in the same chamber or differentchambers. The process shown in FIG. 4F may be performed as part of block201 in a process as shown in FIGS. 2A-2C. In some embodiments, block 450may be performed as part of block 352 in FIGS. 3A-3C, i.e., after amodulation pretreatment. Block 450 may form a differential inhibitionprofile along a feature axis, with block 460 forming a modifieddifferential inhibition profile along the feature axis. FIG. 4I showsdelay time from a deposition-inhibition-deposition process as comparedto a deposition-inhibition-H2 plasma-deposition process. As shown inFIG. 4I, exposure to the H2 plasma reduces the inhibition effect.

Various post-inhibition treatments above may be used to decrease theinhibition effect and can be referred to as “de-inhibition” treatments.FIGS. 4G and 4H are examples of flow charts that show operations inusing such treatments to fill a feature with tungsten. In FIG. 4G,tungsten is deposited in a feature (449). Block 449 involves partiallyfilling the feature with tungsten. In some embodiments, block 449involves depositing a thin conformal film as described above withrespect to block 301 of FIG. 2B. The substrate is then exposed to aninhibition treatment (450) as described above. After exposing thesubstrate to an inhibition treatment, the substrate is exposed to ade-inhibition treatment that reduces the inhibition effect. Examples ofde-inhibition treatments are given above and include an H-containingplasma, a reducing agent thermal soak, and a thermal anneal. Selectivedeposition of tungsten in then performed in accordance with theinhibition profile (203) as described above.

In FIG. 4H, blocks 449 and 450 are performed as described above withrespect to FIG. 4G. After block 450, a selective deposition is performedin accordance with the inhibition profile obtained in block 450 (203).The selective deposition is followed by exposing the substrate to ade-inhibition treatment (458) as described above. Another selectivedeposition of tungsten is performed in accordance with the inhibitionprofile obtained in block 458 (203). In some embodiments, block 458 mayremove the inhibition effect, such the deposition in block 203 is notpreferential or selective to a particular region of the feature.

The process shown in FIG. 4G can be used to reduce the inhibition effectacross all features to be filled on a substrate. The process shown inFIG. 4H allows complete fill of some features, e.g., narrow or highaspect ratio or otherwise challenging features before reducing theinhibition effect on partially filled features.

As described above, aspects of the disclosure can be used for VNANDwordline (WL) fill. While the below discussion provides a framework forvarious methods, the methods are not so limited and can be implementedin other applications as well, including logic and memory contact fill,DRAM buried wordline fill, vertically integrated memory gate/wordlinefill, and 3D integration (TSV).

FIG. 1F, described above, provides an example of a VNAND wordlinestructure to be filled. As discussed above, feature fill of thesestructures can present several challenges including constrictionspresented by pillar placement. In addition, a high feature density cancause a loading effect such that reactants are used up prior to completefill.

Various methods are described below for void-free fill through theentire WL. In certain embodiments, low resistivity tungsten isdeposited. FIG. 5 shows a sequence in which non-conformal selectiveinhibition is used to fill in the interior of the feature before pinchoff. In FIG. 5, a structure 500 is provided with a liner layer surface502. The liner layer surface 502 may be for example, TiN or WN. Next, aW nucleation layer 504 is conformally deposited on the liner layer 502.A PNL process as described above can be used. Note that in someembodiments, this operation of depositing a conformal nucleation layermay be omitted. Next, the structure is exposed to an inhibitionchemistry to selectively inhibit portions 506 of the structure 500. Inthis example, the portions 508 through the pillar constrictions 151 areselectively inhibited. Inhibition can involve for example, exposure to adirect (in-situ) plasma generated from a gas such as N₂, H_(z), forminggas, NH₃, O₂, CH₄, etc. Other methods of exposing the feature toinhibition species are described above. Next, a CVD process is performedto selectively deposit tungsten in accordance with the inhibitionprofile: bulk tungsten 510 is preferentially deposited on thenon-inhibited portions of the nucleation layer 504, such thathard-to-fill regions behind constrictions are filled. The remainder ofthe feature is then filled with bulk tungsten 510. As described abovewith reference to FIG. 2A, the same CVD process used to selectivelydeposit tungsten may be used to remainder of the feature, or a differentCVD process using a different chemistry or process conditions and/orperformed after a nucleation layer is deposited may be used.

In some embodiments, methods described herein may be used for tungstenvia fill. FIG. 6 shows an example of a feature hole 105 including anunderlayer 113, which can be, for example, a metal nitride or otherbarrier layer. A tungsten layer 653 is conformally deposited in thefeature hole 10, for example, by a PNL and/or CVD method. (Note thatwhile the tungsten layer 653 is conformally deposited in the featurehole 105 in the example of FIG. 6, in some other embodiments, tungstennucleation on the underlayer 113 can be selectively inhibited prior toselective deposition of the tungsten layer 653.) Further deposition onthe tungsten layer 653 is then selectively inhibited, forming inhibitedportion 655 of the tungsten layer 653 near the feature opening. Tungstenis then selectively deposited by a PNL and/or CVD method in accordancewith the inhibition profile such that tungsten is preferentiallydeposited near the bottom and mid-section of the feature. Depositioncontinues, in some embodiments with one or more selective inhibitioncycles, until the feature is filled. As described above, in someembodiments, the inhibition effect at the feature top can be overcome bya long enough deposition time, while in some embodiments, an additionalnucleation layer deposition or other treatment may be performed tolessen or remove the passivation at the feature opening once depositionthere is desired. Note that in some embodiments, feature fill may stillinclude formation of a seam, such as seam 657 depicted in FIG. 6. Inother embodiments, the feature fill may be void-free and seam-free. Evenif a seam is present, it may be smaller than obtained with aconventionally filled feature, reducing the problem of coring duringCMP. The sequence depicted in the example of FIG. 6 ends post-CMP with arelatively small void present.

In some embodiments, the processes described herein may be usedadvantageously even for features that do not have constrictions orpossible pinch-off points. For example, the processes may be used forbottom-up, rather than conformal, fill of a feature. FIG. 7 depicts asequence in which a feature 700 is filled by a method according tocertain embodiments. A thin conformal layer of tungsten 753 is depositedinitially, followed by selective inhibition to form inhibited portions755, layer 753 at the bottom of the feature not treated. CVD depositionresults in a bulk film 757 deposited on at the bottom of the feature.This is then followed by repeated cycles of selective CVD deposition andselective inhibition until the feature is filled with bulk tungsten 757.Because nucleation on the sidewalls of the feature is inhibited exceptnear the bottom of the feature, fill is bottom-up. In some embodiments,different parameters may be used in successive inhibitions to tune theinhibition profile appropriately as the bottom of the feature growscloser to the feature opening. For example, a bias power and/ortreatment time may be decreased is successive inhibition treatments.

Experimental

3D VNAND features similar to the schematic depiction in FIG. 1F wereexposed to plasmas generated from N₂H₂ gas after deposition of aninitial tungsten seed layer. The substrate was biased with a DC bias,with bias power varied from 100 W to 700 W and exposure time variedbetween 20 s and 200 s. Longer time resulted in deeper and widerinhibition, with higher bias power resulting in deeper inhibition.

Table 1 shows effect of treatment time. All inhibition treatments usedexposure to a direct LFRF 2000 W N₂H₂ plasma with a DC bias of 100 W onthe substrate.

TABLE 1 Effect of treatment time on inhibition profile InitialInhibition Tungsten Treatment Subsequent Layer Time Deposition SelectiveDeposition A Nucleation + None 400 s CVD at Non-selective 30 s CVD at300° C. deposition 300° C. B same as A 60 s same as A Non-selectivedeposition C same as A 90 s same as A Yes - deposition only from bottomof feature to slightly less than vertical midpoint. Lateral deposition(wider) at bottom of feature. D same as A 140 s  same as A No depositionWhile varying treatment time resulted in vertical and lateral tuning ofinhibition profile as described in Table 1 (split C), varying bias powercorrelated higher to vertical tuning of inhibition profile, with lateralvariation a secondary effect.

As described above, the inhibition effect may be overcome by certain CVDconditions, including longer CVD time and/or higher temperatures, moreaggressive chemistry, etc. Table 2 below, shows the effect of CVD timeon selective deposition.

TABLE 2 Effect of CVD time on selective deposition Subsequent InitialCVD Tungsten Inhibition Deposition Layer Treatment Time (300° C.)Selective Deposition E Nucleation + H₂N₂ 0 no deposition 30 s CVD at2000 W 300° C. RF direct plasma, 90 s, 100 W DC bias F same as E same asE 200 s Yes - small amount of deposition extending about ⅙ height offeature from bottom G same as E same as E 400 s Yes - deposition onlyfrom bottom of feature to slightly less than vertical midpoint. Lateraldeposition wider at bottom of feature. H same as E same as E 700 s Yes -deposition through full height of feature, with lateral deposition widerat bottom of featureApparatus

Any suitable chamber may be used to implement this novel method.Examples of deposition apparatuses include various systems, e.g., ALTUSand ALTUS Max, available from Lam Research, Inc. of Fremont, Calif., orany of a variety of other commercially available processing systems.

FIG. 8 illustrates a schematic representation of an apparatus 800 forprocessing a partially fabricated semiconductor substrate in accordancewith certain embodiments. The apparatus 800 includes a chamber 818 witha pedestal 820, a shower head 814, and an in-situ plasma generator 816.The apparatus 800 also includes a system controller 822 to receive inputand/or supply control signals to various devices.

In certain embodiments, a inhibition gas and, if present, inert gases,such as argon, helium and others, can be supplied to the remote plasmagenerator 806 from a source 802, which may be a storage tank. Anysuitable remote plasma generator may be used for activating the etchantbefore introducing it into the chamber 818. For example, a Remote PlasmaCleaning (RPC) units, such as ASTRON® i Type AX7670, ASTRON® e TypeAX7680, ASTRON® ex Type AX7685, ASTRON® hf-s Type AX7645, all availablefrom MKS Instruments of Andover, Mass., may be used. An RPC unit istypically a self-contained device generating weakly ionized plasma usingthe supplied etchant. Imbedded into the RPC unit a high power RFgenerator provides energy to the electrons in the plasma. This energy isthen transferred to the neutral inhibition gas molecules leading totemperature in the order of 2000K causing thermal dissociation of thesemolecules. An RPC unit may dissociate more than 60% of incomingmolecules because of its high RF energy and special channel geometrycausing the gas to adsorb most of this energy.

In certain embodiments, an inhibition gas is flown from the remoteplasma generator 806 through a connecting line 808 into the chamber 818,where the mixture is distributed through the shower head 814. In otherembodiments, an inhibition gas is flown into the chamber 818 directlycompletely bypassing the remote plasma generator 806 (e.g., the system800 does not include such generator). Alternatively, the remote plasmagenerator 806 may be turned off while flowing the inhibition gas intothe chamber 818, for example, because activation of the inhibition gasis not needed or will be supplied by an in situ plasma generator.

The shower head 814 or the pedestal 820 typically may have an internalplasma generator 816 attached to it. In one example, the generator 816is a High Frequency (HF) generator capable of providing between about 0W and 10,000 W at frequencies between about 1 MHz and 100 MHz. Inanother example, the generator 816 is a Low Frequency (LF) generatorcapable of providing between about 0 W and 10,000 W at frequencies aslow as about 100 KHz. In a more specific embodiment, a HF generator maydeliver between about 0 W to 5,000 W at about 13.56 MHz. The RFgenerator 816 may generate in-situ plasma to active inhibition species.In certain embodiments, the RF generator 816 can be used with the remoteplasma generator 806 or not used. In certain embodiments, no plasmagenerator is used during deposition.

The chamber 818 may include a sensor 824 for sensing various processparameters, such as degree of deposition, concentrations, pressure,temperature, and others. The sensor 824 may provide information onchamber conditions during the process to the system controller 822.Examples of the sensor 824 include mass flow controllers, pressuresensors, thermocouples, and others. The sensor 824 may also include aninfra-red detector or optical detector to monitor presence of gases inthe chamber and control measures.

Deposition and selective inhibition operations can generate variousvolatile species that are evacuated from the chamber 818. Moreover,processing is performed at certain predetermined pressure levels thechamber 818. Both of these functions are achieved using a vacuum outlet826, which may be a vacuum pump.

In certain embodiments, a system controller 822 is employed to controlprocess parameters. The system controller 822 typically includes one ormore memory devices and one or more processors. The processor mayinclude a CPU or computer, analog and/or digital input/outputconnections, stepper motor controller boards, etc. Typically there willbe a user interface associated with system controller 822. The userinterface may include a display screen, graphical software displays ofthe apparatus and/or process conditions, and user input devices such aspointing devices, keyboards, touch screens, microphones, etc.

In certain embodiments, the system controller 822 controls the substratetemperature, inhibition gas flow rate, power output of the remote plasmagenerator 806 and/or in situ plasma generator 816, pressure inside thechamber 818 and other process parameters. The system controller 822executes system control software including sets of instructions forcontrolling the timing, mixture of gases, chamber pressure, chambertemperature, and other parameters of a particular process. Othercomputer programs stored on memory devices associated with thecontroller may be employed in some embodiments.

The computer program code for controlling the processes in a processsequence can be written in any conventional computer readableprogramming language: for example, assembly language, C, C++, Pascal,Fortran or others. Compiled object code or script is executed by theprocessor to perform the tasks identified in the program. The systemsoftware may be designed or configured in many different ways. Forexample, various chamber component subroutines or control objects may bewritten to control operation of the chamber components necessary tocarry out the described processes. Examples of programs or sections ofprograms for this purpose include process gas control code, pressurecontrol code, and plasma control code.

The controller parameters relate to process conditions such as, forexample, timing of each operation, pressure inside the chamber,substrate temperature, inhibition gas flow rates, inhibition modulationgas flow rates, etc. These parameters are provided to the user in theform of a recipe, and may be entered utilizing the user interface.Signals for monitoring the process may be provided by analog and/ordigital input connections of the system controller 822. The signals forcontrolling the process are output on the analog and digital outputconnections of the apparatus 800. Further description of a systemcontroller such as system controller 822 is provided below.

Multi-Station Apparatus

FIG. 9A shows an example of a multi-station apparatus 900. The apparatus900 includes a process chamber 901 and one or more cassettes 903 (e.g.,Front Opening Unified Pods) for holding substrates to be processed andsubstrates that have completed processing. The chamber 901 may have anumber of stations, for example, two stations, three stations, fourstations, five stations, six stations, seven stations, eight stations,ten stations, or any other number of stations. The number of stations inusually determined by a complexity of the processing operations and anumber of these operations that can be performed in a sharedenvironment. FIG. 9A illustrates the process chamber 901 that includessix stations, labeled 911 through 916. All stations in the multi-stationapparatus 900 with a single process chamber 903 are exposed to the samepressure environment. However, each station may have a designatedreactant distribution system and local plasma and heating conditionsachieved by a dedicated plasma generator and pedestal, such as the onesillustrated in FIG. 8.

A substrate to be processed is loaded from one of the cassettes 903through a load-lock 905 into the station 911. An external robot 907 maybe used to transfer the substrate from the cassette 903 and into theload-lock 905. In the depicted embodiment, there are two separate loadlocks 905. These are typically equipped with substrate transferringdevices to move substrates from the load-lock 905 (once the pressure isequilibrated to a level corresponding to the internal environment of theprocess chamber 903) into the station 911 and from the station 916 backinto the load-lock 905 for removal from the processing chamber 903. Amechanism 909 is used to transfer substrates among the processingstations 911-916 and support some of the substrates during the processas described below.

In certain embodiments, one or more stations may be reserved for heatingthe substrate. Such stations may have a heating lamp (not shown)positioned above the substrate and/or a heating pedestal supporting thesubstrate similar to one illustrated in FIG. 8. For example, a station911 may receive a substrate from a load-lock and be used to pre-heat thesubstrate before being further processed. Other stations may be used forfilling high aspect ratio features including deposition and selectiveinhibition operations.

After the substrate is heated or otherwise processed at the station 911,the substrate is moved successively to the processing stations 912, 913,914, 915, and 916, which may or may not be arranged sequentially. Themulti-station apparatus 900 can be configured such that all stations areexposed to the same pressure environment. In so doing, the substratesare transferred from the station 911 to other stations in the chamber901 without a need for transfer ports, such as load-locks.

In certain embodiments, one or more stations may be used to fillfeatures with tungsten-containing materials. For example, stations 912may be used for an initial deposition operation, station 913 may be usedfor a corresponding selective inhibition operation. In the embodimentswhere a deposition-inhibition cycle is repeated, stations 914 may beused for another deposition operations and station 915 may be used foranother inhibition operation. Section 916 may be used for the finalfilling operation. It should be understood that any configurations ofstation designations to specific processes (heating, filling, andremoval) may be used. In some implementations, any of the stations canbe dedicated to one or more of PNL (or ALD) deposition, selectiveinhibition, pre- or post-inhibition modulation treatments, and CVDdeposition.

As an alternative to the multi-station apparatus described above, themethod may be implemented in a single substrate chamber or amulti-station chamber processing a substrate(s) in a single processingstation in batch mode (i.e., non-sequential). In this aspect of theinvention, the substrate is loaded into the chamber and positioned onthe pedestal of the single processing station (whether it is anapparatus having only one processing station or an apparatus havingmulti-stations running in batch mode). The substrate may be then heatedand the deposition operation may be conducted. The process conditions inthe chamber may be then adjusted and the selective inhibition of thedeposited layer is then performed. The process may continue with one ormore deposition-inhibition cycles (if performed) and with the finalfilling operation all performed on the same station. Alternatively, asingle station apparatus may be first used to perform only one of theoperation in the new method (e.g., depositing, selective inhibition,final filling) on multiple substrates after which the substrates may bereturned back to the same station or moved to a different station (e.g.,of a different apparatus) to perform one or more of the remainingoperations.

Multi-Chamber Apparatus

FIG. 9B is a schematic illustration of a multi-chamber apparatus 920that may be used in accordance with certain embodiments. As shown, theapparatus 920 has three separate chambers 921, 923, and 925. Each ofthese chambers is illustrated with two pedestals. It should beunderstood that an apparatus may have any number of chambers (e.g., one,two, three, four, five, six, etc.) and each chamber may have any numberof chambers (e.g., one, two, three, four, five, six, etc.). Each chamber921-525 has its own pressure environment, which is not shared betweenchambers. Each chamber may have one or more corresponding transfer ports(e.g., load-locks). The apparatus may also have a shared substratehandling robot 927 for transferring substrates between the transferports one or more cassettes 929.

As noted above, separate chambers may be used for depositing tungstencontaining materials and selective inhibition of these depositedmaterials in later operations. Separating these two operations intodifferent chambers can help to substantially improve processing speedsby maintaining the same environmental conditions in each chamber. Achamber does not need to change its environment from conditions used fordeposition to conditions used for selective inhibition and back, whichmay involve different chemistries, different temperatures, pressures,and other process parameters. In certain embodiments, it is faster totransfer partially manufactured semiconductor substrates between two ormore different chambers than changing environmental conditions of thesechambers.

FIG. 10 shows a process diagram illustrating operations in a method ofcleaning a deposition chamber. First, a batch of substrates is processedin a tungsten deposition chamber (1001). Block 1001 may involve a CVDprocess as described above, for example. Next, an inhibition treatmentis performed (1003). Examples of inhibition treatments are given above,and include exposure to nitrogen plasmas. A next batch of substrates maythen be processed, with deposition on the chamber inhibited by theinhibition treatment (1005). Block 1003 may be performed with nosubstrate or a dummy substrate present in the chamber. It may also beperformed as part of regular maintenance process that may include any ofcleaning the chamber using an etchant chemistry and depositing a precoator undercoat.

In some implementations, a controller is part of a system, which may bepart of the above-described examples. Such systems can comprisesemiconductor processing equipment, including a processing tool ortools, chamber or chambers, a platform or platforms for processing,and/or specific processing components (a wafer pedestal, a gas flowsystem, etc.). These systems may be integrated with electronics forcontrolling their operation before, during, and after processing of asemiconductor wafer or substrate. The electronics may be referred to asthe “controller,” which may control various components or subparts ofthe system or systems. The controller, depending on the processingrequirements and/or the type of system, may be programmed to control anyof the processes disclosed herein, including power, intensity, andexposure times. In an integrated tool, the controller may also controlprocesses such as processing gases, temperature settings (e.g., heatingand/or cooling), pressure settings, vacuum settings, power settings,radio frequency (RF) generator settings, RF matching circuit settings,frequency settings, flow rate settings, fluid delivery settings,positional and operation settings, wafer transfers into and out of atool and other transfer tools and/or load locks connected to orinterfaced with a specific system.

Broadly speaking, the controller may be defined as electronics havingvarious integrated circuits, logic, memory, and/or software that receiveinstructions, issue instructions, control operation, enable cleaningoperations, enable endpoint measurements, and the like. The integratedcircuits may include chips in the form of firmware that store programinstructions, digital signal processors (DSPs), chips defined asapplication specific integrated circuits (ASICs), and/or one or moremicroprocessors, or microcontrollers that execute program instructions(e.g., software). The system software may be designed or configured inmany different ways. For example, various chamber component subroutinesor control objects may be written to control operation of the chambercomponents necessary to carry out the inventive processes. Examples ofprograms or sections of programs for this purpose include substratepositioning code, treatment compound control code, pressure controlcode, heater control code, and RF control code. In one embodiment, thecontroller includes instructions for performing processes of thedisclosed embodiments according to methods described above. The computerprogram code for controlling the processes can be written in anyconventional computer readable programming language: for example,assembly language, C, C++, Pascal, Fortran, or others. Compiled objectcode or script is executed by the processor to perform the tasksidentified in the program.

Program instructions may be instructions communicated to the controllerin the form of various individual settings (or program files), definingoperational parameters for carrying out a particular process on or for asemiconductor wafer or to a system. The operational parameters may, insome embodiments, be part of a recipe defined by process engineers toaccomplish one or more processing steps during the fabrication of one ormore layers, materials, metals, oxides, silicon, silicon dioxide,surfaces, circuits, and/or dies of a wafer.

The controller, in some implementations, may be a part of or coupled toa computer that is integrated with, coupled to the system, otherwisenetworked to the system, or a combination thereof. For example, thecontroller may be in the “cloud” or all or a part of a fab host computersystem, which can allow for remote access of the wafer processing. Thecomputer may enable remote access to the system to monitor currentprogress of fabrication operations, examine a history of pastfabrication operations, examine trends or performance metrics from aplurality of fabrication operations, to change parameters of currentprocessing, to set processing steps to follow a current processing, orto start a new process. In some examples, a remote computer (e.g. aserver) can provide process recipes to a system over a network, whichmay include a local network or the Internet. The remote computer mayinclude a user interface that enables entry or programming of parametersand/or settings, which are then communicated to the system from theremote computer. In some examples, the controller receives instructionsin the form of data, which specify parameters for each of the processingsteps to be performed during one or more operations. It should beunderstood that the parameters may be specific to the type of process tobe performed and the type of tool that the controller is configured tointerface with or control. Thus as described above, the controller maybe distributed, such as by comprising one or more discrete controllersthat are networked together and working towards a common purpose, suchas the processes and controls described herein. An example of adistributed controller for such purposes would be one or more integratedcircuits on a chamber in communication with one or more integratedcircuits located remotely (such as at the platform level or as part of aremote computer) that combine to control a process on the chamber.

Without limitation, example systems may include a plasma etch chamber ormodule, a deposition chamber or module, a spin-rinse chamber or module,a metal plating chamber or module, a clean chamber or module, a beveledge etch chamber or module, a physical vapor deposition (PVD) chamberor module, a chemical vapor deposition (CVD) chamber or module, anatomic layer deposition (ALD) chamber or module, an atomic layer etch(ALE) chamber or module, an ion implantation chamber or module, a trackchamber or module, and any other semiconductor processing systems thatmay be associated or used in the fabrication and/or manufacturing ofsemiconductor wafers.

As noted above, depending on the process step or steps to be performedby the tool, the controller might communicate with one or more of othertool circuits or modules, other tool components, cluster tools, othertool interfaces, adjacent tools, neighboring tools, tools locatedthroughout a factory, a main computer, another controller, or tools usedin material transport that bring containers of wafers to and from toollocations and/or load ports in a semiconductor manufacturing factory.There may be a user interface associated with controller. The userinterface may include a display screen, graphical software displays ofthe apparatus and/or process conditions, and user input devices such aspointing devices, keyboards, touch screens, microphones, etc.

Patterning Method/Apparatus:

The apparatus/process described hereinabove may be used in conjunctionwith lithographic patterning tools or processes, for example, for thefabrication or manufacture of semiconductor devices, displays, LEDs,photovoltaic panels and the like. Typically, though not necessarily,such tools/processes will be used or conducted together in a commonfabrication facility. Lithographic patterning of a film typicallycomprises some or all of the following steps, each step enabled with anumber of possible tools: (1) application of photoresist on a workpiece,i.e., substrate, using a spin-on or spray-on tool; (2) curing ofphotoresist using a hot plate or furnace or UV curing tool; (3) exposingthe photoresist to visible or UV or x-ray light with a tool such as awafer stepper; (4) developing the resist so as to selectively removeresist and thereby pattern it using a tool such as a wet bench; (5)transferring the resist pattern into an underlying film or workpiece byusing a dry or plasma-assisted etching tool; and (6) removing the resistusing a tool such as an RF or microwave plasma resist stripper.

The invention claimed is:
 1. A method comprising: providing a substrateincluding a feature having one or more feature openings and a featureinterior; exposing the feature to at least one of: an oxidizingenvironment, a vacuum break, a reducing agent soak, and atungsten-containing agent soak; after exposing the feature and prior todepositing tungsten in the feature, selectively inhibiting tungstennucleation in the feature such that there is a differential inhibitionprofile along a feature axis; and selectively depositing tungsten in thefeature in accordance with the differential inhibition profile, whereinexposing the feature comprises exposing a tungsten bulk layer or anon-tungsten surface to the at least one of an oxidizing environment, avacuum break, a reducing agent soak, and a tungsten-containing agentsoak.
 2. The method of claim 1, wherein selectively inhibiting tungstennucleation in the feature comprises exposing the feature to a directplasma while applying a bias to the substrate.
 3. The method of claim 2,wherein the plasma contains one or more of nitrogen, hydrogen, oxygenand carbon activated species.
 4. The method of claim 1, whereinselectively inhibiting tungsten nucleation in the feature comprises anon-plasma process.
 5. The method of claim 4, wherein the non-plasmaprocess comprises exposing the feature to a non-plasmanitrogen-containing gas.
 6. The method of claim 1, wherein exposing thefeature to one of: an oxidizing environment, a vacuum break, a reducingagent soak, and a tungsten-containing agent soak comprises a reducingagent soak.
 7. The method of claim 6, wherein the reducing agent is oneof a diborane and silane.
 8. The method of claim 1, wherein selectivelyinhibiting tungsten nucleation in the feature comprises exposing thefeature to a remote plasma.
 9. The method of claim 6, wherein thereducing agent soak comprises adsorbing reducing agent species on thefeature surface.
 10. The method of claim 9, wherein the reducing agentsoak increases the inhibition.
 11. The method of claim 1, whereinexposing the feature to one of: an oxidizing environment, a vacuumbreak, a reducing agent soak, and a tungsten-containing agent soakcomprises exposing the feature to an oxidizing environment.
 12. Themethod of claim 1, wherein exposing the feature to one of: a vacuumbreak, a reducing agent soak, and a tungsten-containing agent soakcomprises exposing the feature to a vacuum break.
 13. The method ofclaim 1, wherein exposing the feature to one of: an oxidizingenvironment, a vacuum break, a reducing agent soak, and atungsten-containing agent soak comprises exposing the feature to atungsten-containing agent soak.